Strengthening with bonded pre-stressed FRP composite laminates

Using bonded fiber reinforced polymer (FRP) laminates for strengthening and repair of structural members has been proven to be an effective and economic method.

High strength and stiffness, light weight and good fatigue and durability properties of FRP composites together with advantages offered by adhesive bonding have made it a suitable alternative for traditional strengthening and repair techniques. It has also been recognized that pre-stressing the FRP laminates prior to bonding would bring additional advantages such as reduced crack widths, postponing the yielding in tensile reinforcement, increasing the load bearing capacity and saving reinforcement material.

Using pre-stressed laminates, however, is associated with very high interfacial stresses in the bond line at the laminate ends, which necessitates the use of mechanical anchors. This project presents a new method and a device for applying pre-stressed FRP laminates to flexural structural members without the need for mechanical anchorage of the laminates. The principle of the method is based on controlling the interfacial stresses in the bond line using a non-uniform pre-stressing force profile. The principle of the method along with lab verifications and field applications are presented and discussed.